1. Field
Exemplary embodiments relate to a semiconductor photo-detecting device. More particularly, exemplary embodiments relate to a semiconductor photo-detecting device with excellent detection efficiency for a specific wavelength of light.
2. Discussion of the Background
Semiconductor photo-detecting devices operate on the principle that current is induced by illuminated light. In particular, semiconductor photo-detecting devices for detecting ultraviolet (UV) light may be used in a variety of fields, such as business, medical science, defense industry, communications, etc. The semiconductor photo-detecting devices are based on the principle that a depletion region is formed by the separation of electrons and holes within a semiconductor upon absorption of photons, and current is, thus, induced depending upon a flow of the electrons.
Semiconductor photo-detecting devices using silicon have been typically used in the art. However, the semiconductor photo-detecting devices may require high voltage for operation and have low detection efficiency. Particularly, when the semiconductor photo-detecting devices for detecting UV light are manufactured using silicon, photo-detection efficiency may decrease due to the silicon being sensitive not only to UV light but also to visible and infrared light. In addition, UV light detecting devices using silicon may be thermally and chemically unstable.
To address such issues, photo-detecting devices using nitride-based semiconductors have been developed. Photo-detecting devices using nitride-based semiconductors may have relatively high responsivity, high reaction rate, low noise level, and high thermal and chemical stability compared with photo-detecting devices using silicon. Photo-detecting devices using AlGaN, among nitride-based semiconductors, as a light absorption layer may show improved characteristics as a UV light detecting device.
Nitride-based semiconductor photo-detecting devices may be manufactured in a variety of structures, such as, photoconductors, Schottky junction photo-detecting devices, p-i-n photo-detecting devices, and the like. Among the various forms of nitride-based semiconductor photo-detecting devices, Schottky junction photo-detecting devices may include a substrate, a buffer layer on the substrate, a light absorption layer on the buffer layer, and a Schottky junction layer on the light absorption layer. Further, a first electrode and a second electrode may be arranged on the Schottky junction layer and the buffer layer or the light absorption layer, respectively. To use the Schottky junction photo-detecting device as a UV light detecting device, the light absorption layer may be formed of a nitride-based semiconductor having band gap energy capable of absorbing UV light. Accordingly, AlGaN may be used as a semiconductor substance in the light absorption layer. A GaN layer may be used as the buffer layer.
In a structure including an AlGaN light absorption layer and a GaN buffer layer, when the AlGaN light absorption layer has an Al composition of 25% or more, or a thickness of 0.1 μm or more, cracks may be generated in the light absorption layer, thereby causing a yield decrease. To prevent cracking in the light absorption layer, an AlN layer may be interposed between the GaN buffer layer and the AlGaN light absorption layer. Even in this case, photo-detection response may be reduced due to high energy band gap and insulation characteristics of the AlN layer. Specifically, when the thickness of the AlN layer is less than about 100 Å, photo-detection characteristics may be improved but it may be difficult to completely prevent cracks, and when the thickness of the AlN layer exceeds about 100 Å, cracks may be prevented, but photo-detection characteristics may be deteriorated.
In addition, GaN, InGaN, and AlGaN layers used as a light absorption layer in typical nitride-based semiconductor photo-detecting devices may have intrinsic defects and allow current flow in the devices in response to visible light, but not UV light due to such defects. In response, characteristics of the semiconductor photo-detecting device, a low UV-to-visible rejection ratio of about 103 has been measured. That is, the typical semiconductor photo-detecting devices may allow low current flow in response to visible light but not UV light, thereby, deteriorating detection accuracy.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the inventive concept, and therefore, it may contain information that does not form any part of the prior art that is already known in this country to a person of ordinary skill in the art.